Disposable Immunochips for the Detection of Legionella pneumophila Using Electrochemical Impedance Spectroscopy Nan Li,† Arujun Brahmendra,‡ Anthony J. Veloso,† Akriti Prashar,‡ Xin R. Cheng,† Vinci W. S. Hung,† Cyril Guyard,§,⊥ Mauricio Terebiznik,‡ and Kagan Kerman*,†,‡ †
Department of Physical and Environmental Sciences, ‡Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada § Ontario Agency for Health Protection and Promotion (OAHPP), 81A Resource Road, Toronto, ON, M9P 3T1, Canada ⊥ Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, M5S 1A8, Canada S * Supporting Information
ABSTRACT: The rapid diagnosis of Legionellosis is crucial for the effective treatment of this disease. Currently, most clinical laboratories utilize rapid immunoassays that are sufficient for the detection of Legionella serogroup 1, but not other clinically relevant serogroups. In this report, the development of a disposable immunochip system is described in connection with electrochemical impedance spectroscopy and fluorescence microscopy. The immunochips were prepared by covalently immobilizing fluorophore-conjugated L. pneumophila antibodies on Au chips. The analytical performance of the immunochips was optimized as a prescreening tool for L. pneumophila. The versatile immunochips described here can be easily adapted for the monitoring of all Legionella serogroups in clinical and environmental samples.
he genus Legionella pneumophila comprises more than 50 species and 70 serogroups that inhabit natural and human engineered aquatic environments.1 A review of drinking waterassociated diseases in United States showed that Legionella accounted for 29% of outbreaks from 2001 to 2006.2 Legionella is parasitic in protozoan organisms and infects humans through the inhalation of contaminated aerosolized droplets of water. This opportunistic pathogen targets respiratory tissue causing a severe pneumonia known as Legionnaires’ disease and the lesser form, Pontiac fever.3,4 According to World Health Organization (WHO), mortality rate associated with Legionnaires’ disease is up to 40% among average patients and up to 80% among immuno-suppressed patients. Since death by Legionella infection depends on the early antimicrobial treatment, rapid diagnosis of this disease is critical for efficient treatment and patient survival. Epidemiological data indicates that L. pneumophila is responsible for 91.5% of diagnosed Legionellosis cases and that serogroup 1 (Lp1) is the predominant serotype found in North America and Europe.4 Studies by the Ontario Agency for Health Protection and Promotion (OAHPP) showed that 39% of the culture-confirmed Legionellosis reported over the last three decades in Ontario were caused by serogroups different from Lp1.5,6 Conventional detection tests use Legionella culture, direct immunofluorescence assay, urinary antigen test, serology testing, or polymerase chain reaction.1 However, these methods have turnaround times measurable in several hours to days, are expensive, are technically demanding, and are limited in their detection of different serogroups. Here, we propose a low-cost © 2012 American Chemical Society
and miniaturized electrochemical system that requires an incubation time of approximately 1 h, does not require a strong technical expertise, and has the potential to detect various L. pneumophila serogroups. Tremendous amounts of research activities have been carried out in the past decade toward the miniaturization of electrochemical chips and toward the development of hand-held devices.7−14 These disposable screen-printed chips can be mass produced at low cost, and each experiment can be performed on a fresh and analogous surface to prevent possible cross-contamination errors. Each electrode can be disposed after use, and that can eliminate carry-over contamination from tedious...